French gold open faced pocket watch with châtelaine Circa 1854

Gold pocket watch with open face by Le Roy & Fils
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Extremely rare and fine, open faced, round-shaped, key-winding Swiss pendant watch with its châtelaine, in 18K yellow gold, enamel, silver and diamonds, circa 1854.
Polished 18K gold case. Gilded brass movement with going barrel, cylinder escapement, monometallic balance (gilded brass) and blued steel flat hairspring. Enamel dial with Roman radial hours, outer minutes track, and gold Breguet hands. Signature on the cuvette, and accompanied by matching châtelaine, breloques (including key-winding) and certificate.
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Diameter: 30.2 mm
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Weight: 68.6 g
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Signed: Le Roy & Fils
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The Leroy Certificate, dated June 4, 2019, mentioned that this watch was sold on October 6, 1854, to Monsieur Bapst fils (probably the Parisian goldsmith), for 400 Francs.
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The London branch of the Paris firm of Le Roy & Fils (which derived from the business established by Basile Charles Le Roy, c. 1785) was set up at the latest by 1854 in 296 Regent Street. By 1866 they had also acquired 211 Regent Street, and by 1875 occupied both 211 & 213. By 1885 they had moved to 57 Bond Street, in which elegant thoroughfare they remained until 1952.